Resin composition, resin molded article, and method of preparing resin composition

ABSTRACT

A resin composition includes a cellulose derivative in which at least one hydroxyl group is substituted with an acyl group, which has a weight average molecular weight of 10,000 to 75,000 and an average degree of substitution of the acyl group of 1.8 to 2.5, and which exhibits an amount (weight ratio) of an insoluble portion, when being dissolved in tetrahydrofuran (THF) at 25° C., of less than or equal to 5% by weight.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based on and claims priority under 35 USC 119 fromJapanese Patent Application No. 2016-062524 filed Mar. 25, 2016.

BACKGROUND

1. Technical Field

The present invention relates to a resin composition, a resin moldedarticle, and a method of preparing a resin composition.

2. Related Art

In recent years, various resin compositions have been provided and havebeen used for various applications. Particularly, the resin compositionshave been used in various components or housings or the like of homeappliances or vehicles, or thermoplastic resins have also been used incomponents such as housings of business machines or electric andelectronic apparatuses.

In recent years, plant-derived resins have been used, and there is acellulose derivative as one of the plant-derived resins which have beenknown.

SUMMARY

According to an aspect of the invention, there is provided a resincomposition including a cellulose derivative in which at least onehydroxyl group is substituted with an acyl group, which has a weightaverage molecular weight of 10,000 to 75,000 and an average degree ofsubstitution of the acyl group of 1.8 to 2.5, and which exhibits anamount (weight ratio) of an insoluble portion, when being dissolved intetrahydrofuran (THF) at 25° C., of less than or equal to 5% by weight.

DETAILED DESCRIPTION

Hereinafter, an exemplary embodiment of a resin composition and a resinmolded article of the invention will be described.

Resin Composition

The resin composition according to the exemplary embodiment contains acellulose derivative in which at least one hydroxyl group is substitutedwith an acyl group, which has a weight average molecular weight of10,000 to 75,000 and an average degree of substitution of the acyl groupof 1.8 to 2.5.

The amount (weight ratio) of an insoluble portion of this cellulosederivative when being dissolved in tetrahydrofuran (THF) at 25° C. isless than or equal to 5% by weight.

According to the resin composition relating to the exemplary embodiment,a resin molded article having excellent strength may be obtained.

The reason why such an effect is exhibited is inferred as follows.

In general, a resin molded article provided with excellent strength andheat resistance may be obtained from the viewpoint of characteristics ofthe chemical structure of a cellulose derivative or characteristics inwhich a hydrogen bonding force in or between molecules is strong.However, the thermal fluidity (that is, low melt viscosity when heat isapplied) is low, and therefore, improvement in molding suitability whenperforming molding through heating and melting is desired.

In contrast, in the resin composition according to the exemplaryembodiment, the weight average molecular weight of a cellulosederivative is within the range. In general, there is a tendency that thestrength of a resin decreases as the molecular weight decreases. As themolecular weight of a cellulose derivative decreases, the number ofterminals of the molecular chain relatively increases and the number ofhydroxyl groups existing at these terminals also increases. For thisreason, even if the weight average molecular weight of the cellulosederivative is as low as less than or equal to 75,000, a hydrogen bond isformed between hydroxyl groups at the terminals after molding in thecellulose derivative, and therefore, it is considered that the strength(for example, elastic modulus or tensile strength) is improved due tohigh hydrogen bonding force.

In contrast, the hydrogen bond between the terminals is weakened whenbeing heated and melted. Therefore, the viscosity decreases due to theweight average molecular weight of the cellulose derivative being withinthe range, thereby improving thermal fluidity.

However, even in a case where the weight average molecular weight of thecellulose derivative is controlled within the range, in some cases,elastic modulus or tensile strength decreases, and therefore, furtherimprovement in the strength is desired.

In contrast, in the exemplary embodiment, the strength of a resin moldedarticle is improved by adjusting the amount (weight ratio) of aninsoluble portion with respect to tetrahydrofuran (THF) at 25° C. to theamount falling within the range.

Here, in the cellulose derivative which is substituted with an acylgroup and of which the average degree of substitution thereof is withinthe range, it is considered that the amount of the insoluble portionwith respect to tetrahydrofuran (THF) at 25° C. being within the rangeis an indicator that the proportion of the cellulose derivative having adegree of substitution exceeding 2.5 is reduced.

It is considered that, in the cellulose derivative of which the degreeof substitution exceeds 2.5, an interaction between substituents becomesstrong, and the mobility of molecules decreases, and therefore, thecellulose derivative hardly forms an intramolecular hydrogen bond. As aresult, elastic modulus decreases and strength also decreases. In theexemplary embodiment, it is considered that the proportion of thecellulose derivative of which the degree of substitution exceeds 2.5 isreduced. Therefore, inhibition of the intramolecular hydrogen bond inthe cellulose derivative is prevented and the elastic modulus increases.As a result, excellent strength may be obtained.

THF Insoluble Portion

The amount (weight ratio) of an insoluble portion of the cellulosederivative in the exemplary embodiment with respect to tetrahydrofuran(THF) at 25° C. is less than or equal to 5% by weight. If the THFinsoluble portion exceeds 5% by weight, the strength deteriorates when aresin molded article is obtained.

It is preferable that the amount of the THF insoluble portion is furtherless than or equal to 3% by weight, and it is more preferable that theamount of the THF insoluble portion is less than or equal to 2% byweight.

A method of measuring the insoluble portion of the cellulose derivativewith respect to tetrahydrofuran (THF) will be described below.

DMSO Insoluble Portion

The amount (weight ratio) of the insoluble portion of the cellulosederivative in the exemplary embodiment with respect to dimethylsulfoxide (DMSO) at 25° C. is preferably less than or equal to 1% byweight.

Excellent strength may be obtained when a resin molded article isobtained by making the DMSO insoluble portion be less than or equal to1% by weight.

Here, in the cellulose derivative which is substituted with an acylgroup and of which the average degree of substitution thereof is withinthe range, it is considered that the amount of the insoluble portionwith respect to dimethyl sulfoxide (DMSO) at 25° C. being within therange is an indicator that the proportion of the cellulose derivative ofwhich the degree of substitution is less than 1.8 is reduced.

It is considered that, in the cellulose derivative of which the degreeof substitution is less than 1.8, an interaction between substituentsbecomes weak, and therefore, causes plasticization. As a result, elasticmodulus decreases and the strength also decreases. If the DMSO insolubleportion is within the above-described range, it is considered that theproportion of the cellulose derivative of which the degree ofsubstitution is less than 1.8 is reduced. Therefore, plasticization inthe cellulose derivative is prevented and the elastic modulus increases.As a result, excellent strength may be obtained.

It is preferable that the amount of the DMSO insoluble portion isfurther less than or equal to 0.8% by weight, and it is more preferablethat the amount of the DMSO insoluble portion is less than or equal to0.5% by weight.

A method of measuring the insoluble portion of the cellulose derivativewith respect to dimethyl sulfoxide (DMSO) will be described below.

Control Method

Here, in a cellulose derivative of which the average degree ofsubstitution of an acyl group is 1.8 to 2.5, examples of the method ofcontrolling the amount of the insoluble portion with respect totetrahydrofuran (THE) and the amount of the insoluble portion withrespect to dimethyl sulfoxide (DMSO) at 25° C. within the range includea method of reducing the amount of a cellulose derivative of which thedegree of substitution using an acyl group is high and a cellulosederivative of which the degree of substitution using an acyl group islow. That is, examples thereof include a method of narrowing thedistribution of the degree of substitution using an acyl group (settingthe cellulose derivative to have sharp substitution distribution).

Specific methods are not particularly limited. However, examples of themethod include a method of adjusting the amount of sulfuric acid whenpreparing a cellulose derivative through esterification by substitutingcellulose with an acyl group. In the case where the amount of sulfuricacid is made larger, substitution with an acyl group is performed almostuniformly, so that a cellulose derivative having a narrower distributionof the degree of substitution is obtained.

Specifically, when esterifying cellulose by substituting the cellulosewith an acyl group, the existing amount of sulfuric acid with respect to100 parts by weight of a solid content of the cellulose is preferably 6parts by weight to 20 parts by weight, more preferably 7 parts by weightto 18 parts by weight, and still more preferably 8 parts by weight to 15parts by weight.

Hereinafter, components of the resin composition according to theexemplary embodiment will be described.

Cellulose Derivative

Weight Average Molecular Weight

The weight average molecular weight of the cellulose derivative used inthe exemplary embodiment is 10,000 to 75,000. This weight averagemolecular weight is still more preferably 20,000 to 50,000.

If the weight average molecular weight exceeds 75,000, the elasticmodulus decreases and heat resistance or thermal fluidity alsodeteriorates. In contrast, if the weight average molecular weight isless than 10,000, the molecular weight is too low, and therefore, theelastic modulus decreases and the heat resistance also decreases.

Here, the weight average molecular weight (Mw) is a value measuredthrough gel permeation chromatography (GPC). Specifically, themeasurement of the molecular weight performed through GPC is carried outusing a GPC device (manufactured by Tosoh Corporation, HLC-8320GPC,column: TSKgel α-M) using a solution of dimethylacetamide/lithiumchloride having a weight ratio of 90/10.

Structure

The cellulose derivative is a cellulose derivative which is obtained byesterifying cellulose with at least an acyl group, and specific examplesthereof include a cellulose derivative represented by the formula (1).

R¹, R², and R³ in the formula (1) each independently represent ahydrogen atom or an acyl group. n represents an integer of 2 or greater.However, at least one of n numbers of R¹s, n numbers of R²s, or nnumbers of R³s represents an acyl group.

The acyl group represented by R¹, R², and R³ is still more preferably anacyl group having 1 to 6 carbon atoms.

In the formula (1), the range of n is not particularly limited, but ispreferably 40 to 300 and is more preferably 100 to 200.

If n is greater than or equal to 40, the strength of a resin moldedarticle easily increases. If n is less than or equal to 300,deterioration in flexibility of the resin molded article is easilyprevented.

Acyl Group

In the cellulose derivative used in the exemplary embodiment, at leastone hydroxyl group is substituted with an acyl group (more preferably,an acyl group having 1 to 6 carbon atoms). That is, in a case of thecellulose derivative having the structure represented by the formula(1), at least one of n numbers of R¹s, n numbers of R²s, or n numbers ofR³s represents an acyl group.

Accordingly, all of or a part of n numbers of R¹s in the cellulosederivative represented by the formula (1) may be the same as ordifferent from each other. Similarly, all of or apart of n numbers ofR²s and R³s may be the same as or different from each other. At leastone thereof represents an acyl group.

With respect to the cellulose derivative having an acyl group having 1to 6 carbon atoms, the elastic modulus increases and the heat resistanceis also improved, compared to a case where all acyl groups substitutingfor the cellulose derivative have greater than or equal to 7 carbonatoms.

The number of carbon atoms of the acyl group substituting for thecellulose derivative is preferably 2 to 4 and more preferably 2 to 3.

The acyl group is represented by a structure of “—CO—R_(AC)”, and R_(AC)represents a hydrogen atom or a hydrocarbon group (more preferably ahydrocarbon group having 1 to 5 carbon atoms).

The hydrocarbon group represented by R_(AC) may be any of a linear,branched, or cyclic group, and is more preferably a linear group.

In addition, the hydrocarbon group may be a saturated hydrocarbon groupor an unsaturated hydrocarbon group, and is more preferably a saturatedhydrocarbon group.

In addition, the hydrocarbon group may have atoms (for example, oxygenor nitrogen) other than a carbon atom and a hydrogen atom, and is morepreferably a hydrocarbon group consisting of a carbon atom and ahydrogen atom.

Examples of the acyl group include a formyl group, an acetyl group, apropionyl group, a butyryl group (butanoyl group), a propenoyl group,and a hexanoyl group.

Among these, an acetyl group is preferable from the viewpoints ofimproving elastic modulus and heat resistance and improving moldabilityof a resin composition.

Average Degree of Substitution

The average degree of substitution of a cellulose derivative is from 1.8to 2.5. Furthermore, a range of 2 to 2.5 is more preferable and a rangeof 2.2 to 2.5 is still more preferable.

By setting the average degree of substitution to less than or equal to2.5, an interaction between substituents does not become too strong anddeterioration of the mobility of molecules is prevented. Therefore, ahydrogen bond is easily formed between molecules, and thus, the elasticmodulus is more increased and the heat resistance is also moreincreased. In contrast, by setting the average degree of substitution togreater than or equal to 1.8, an interaction between molecules does notbecome too weak and plasticization is prevented. As a result, theelastic modulus is more increased and the heat resistance is moreincreased.

The average degree of substitution is an indicator showing the degree ofacylation of a cellulose derivative. Specifically, the average degree ofsubstitution means the intramolecular average of the number of times ofsubstitution in which three hydroxyl groups by a D-glucopyranose unit ofthe cellulose derivative are substituted with acyl groups.

Synthesis Method

The cellulose derivative used in the exemplary embodiment is notparticularly limited, but is synthesized through, for example, thefollowing method.

Adjustment of Molecular Weight of Cellulose

First, cellulose before acylation, that is, cellulose in which hydroxylgroups are not substituted with acyl groups is prepared, and themolecular weight thereof is adjusted.

Prepared cellulose or commercially available cellulose may be used asthe cellulose before the acylation. In general, cellulose is aplant-derived resin, and the weight average molecular weight thereof isgenerally higher than that of the cellulose derivative in the exemplaryembodiment. For this reason, the adjustment of the molecular weight ofcellulose generally becomes a step of reducing the molecular weight.

For example, the weight average molecular weight of commerciallyavailable cellulose is generally within a range of 150,000 to 500,000.

Examples of the commercially available products of the cellulose beforeacylation include KC flock W50, W100, W200, W300G, W400G, W-100F, W60MG,W-50GK, W-100GK, NDPT, NDPS, LNDP, and NSPP-HR manufactured by NipponPaper Industries Co., Ltd.

The method of adjusting the molecular weight of the cellulose before theacylation is not particularly limited, but examples thereof include amethod of reducing the molecular weight by stirring the cellulose in aliquid.

It is possible to adjust the molecular weight of cellulose to a desiredvalue by adjusting the speed, time, or the like during the stirring. Thestirring speed during the stirring is not particularly limited, but ispreferably within a range of 50 rpm to 3,000 rpm and more preferablywithin a range of 100 rpm to 1,000 rpm. In addition, the stirring timeis preferably within a range of 1 hour to 48 hours and more preferablywithin a range of 2 hours to 24 hours.

Examples of the liquid used during the stirring include an aqueoushydrochloric acid solution, an aqueous formic acid solution, an aqueousacetic acid solution, an aqueous nitric acid solution, and an aqueoussulfuric acid solution.

Preparation of Cellulose Derivative

A cellulose derivative may be obtained by acylating cellulose, of whichthe molecular weight is adjusted through the above-described method orthe like, using an acyl group through a well-known method.

In a case where a part of hydroxyl groups which the cellulose has issubstituted with an acetyl group, examples of the method include amethod or the like of esterifying cellulose using a mixture of aceticacid, acetic anhydride, and sulfuric acid. In addition, examples of themethod include an esterification method using propionic anhydrideinstead of acetic anhydride of the mixture in a case where the part ofhydroxyl groups is substituted with a propionyl group; an esterificationmethod using butyl anhydride instead of acetic anhydride of the mixturein a case where the part of hydroxyl groups is substituted with abutanoyl group; an esterification method using hexanoic anhydrideinstead of acetic anhydride of the mixture in a case where the part ofhydroxyl groups is substituted with a hexanoyl group.

In the step of acylating cellulose with an acyl group, it is preferableto adjust the amount of sulfuric acid from the viewpoint of controllingthe amount of an insoluble portion with respect to tetrahydrofuran (THF)and the amount of an insoluble portion with respect to dimethylsulfoxide (DMSO) at 25° C. within the range. In the case where theamount of sulfuric acid is made larger, substitution with an acyl groupis performed almost uniformly, so that a cellulose derivative having anarrower distribution of the degree of substitution is obtained and theTHF insoluble portion and the DMSO insoluble portion are controlledwithin the ranges, respectively.

Specifically, it is preferable that the amount of sulfuric acid withrespect to the solid content of cellulose when esterifying the celluloseby substituting the cellulose with an acyl group is within theabove-described range.

After the acylation, a deacylation step may be further provided for thepurpose of adjusting the average degree of substitution. In addition, apurification step may be further provided after the acylation step orthe deacylation step.

Ratio of Cellulose Derivative Occupied in Resin Composition

The ratio of a cellulose derivative occupied in the total amount of theresin composition according to the exemplary embodiment is preferablygreater than or equal to 70% by weight and more preferably greater thanor equal to 80% by weight. By making the ratio be greater than or equalto 70% by weight, the elastic modulus is more increased and the heatresistance is also more increased.

Plasticizer

The resin Composition according to the exemplary embodiment may furthercontain a plasticizer.

The content of the plasticizer is preferably an amount in which theratio of the cellulose derivative occupied in the total amount of theresin composition becomes within the above-described range. Morespecifically, the ratio of the plasticizer occupied in the total amountof the resin composition is preferably less than or equal to 15% byweight, more preferably less than or equal to 10% by weight, and stillmore preferably less than or equal to 5% by weight. By setting the ratioof the plasticizer to be within the above-described range, the elasticmodulus is more increased and the heat resistance is also moreincreased. In addition, bleeding of the plasticizer is also prevented.

Examples of the plasticizer include an adipic acid ester-containingcompound, a polyether ester compound, a sebacic acid ester compound, aglycol ester compound, acetic acid ester, a dibasic acid ester compound,a phosphate ester compound, a phthalic acid ester compound, camphor,citric acid ester, stearic acid ester, metallic soap, polyols, andpolyalkylene oxide.

Among these, an adipic acid ester-containing compound and a polyetherester compound are preferable and an adipic acid ester-containingcompound is more preferable.

Adipic Acid Ester-Containing Compound

An adipic acid ester-containing compound (compound containing adipicacid ester) indicates a single compound of adipic acid ester, or amixture of adipic acid ester and components (compounds different fromadipic acid ester) other than adipic acid ester. However, the adipicacid ester-containing compound may contain greater than or equal to 50%by weight of adipic acid ester with respect to the total components.

As the adipic acid ester, for example, adipic acid diester, and adipicacid polyester are exemplified. Specifically, adipic acid diesterrepresented by the formula (2-1) and adipic acid polyester representedby the formula (2-2) are exemplified.

In the formulae (2-1) and (2-2), R⁴ and R⁵ each independently representsan alkyl group, or a polyoxyalkyl group [—(C_(x)H_(2x)—O)_(y)—R^(A1)](provided that R^(A1) represents an alkyl group, x represents an integerin the range of 1 to 10, and y represents an integer in the range of 1to 10).

R⁶ represents an alkylene group.

m1 represents an integer in the range of 1 to 20.

m2 represents an integer in the range of 1 to 10.

In the formulae (2-1) and (2-2), the alkyl groups represented by R⁴ andR⁵ are preferably alkyl groups having 1 to 6 carbon atoms, and morepreferably alkyl groups having 1 to 4 carbon atoms. The alkyl groupsrepresented by R⁴ and R⁵ may have anyone of a linear shape, a branchedshape, or a cyclic shape, but preferably a linear shape and a branchedshape.

In the formulae (2-1) and (2-2), in the polyoxyalkyl group representedby R⁴ and R⁵ [—(C_(x)H_(2x)—O)_(y)—R^(A1)] the alkyl group representedby R^(A1) is preferably an alkyl group having 1 to 6 carbon atoms, andmore preferably an alkyl group having 1 to 4 carbon atoms. The alkylgroup represented by R^(A1) may have any one of a linear shape, abranched shape, or a cyclic shape, but preferably a linear shape and abranched shape.

In the formula (2-2), the alkylene group represented by R⁶ is preferablyan alkylene group having 1 to 6 carbon atoms, and more preferably analkylene group having 1 to 4 carbon atoms. The alkylene grouprepresented by R⁶ may have any one of a linear shape, a branched shape,or a cyclic shape, but preferably a linear shape and a branched shape.

In the formulae (2-1) and (2-2), the group represented by each ofsymbols R⁴ to R⁶ may be substituted with a substituent. As thesubstituent, an alkyl group, an aryl group, and a hydroxyl group areexemplified.

The molecular weight of the adipic acid ester (or weight averagemolecular weight) is preferably in the range of 200 to 5,000, and morepreferably in the range of 300 to 2,000. The weight average molecularweight is a value measured according to the method of measuring theweight average molecular weight of the cellulose derivative describedabove.

Specific examples of the adipic acid ester-containing compound aredescribed below, but the examples are not limited thereto.

Name of Material Name of Product Manufacturer ADP1 Adipic acid Daifatty101 Daihachi Chemical diester Industry Co., Ltd. ADP2 Adipic acid AdekaCizer ADEKA Corporation diester RS-107 ADP3 Adipic acid Polycizer DICCorporation polyester W-230-H

Polyether Ester Compound

As the polyether ester compound, for example, a polyether ester compoundrepresented by the formula (3) is exemplified.

In the formula (3), R⁷ and R⁸ each independently represent an alkylenegroup having 2 to 10 carbon atoms. A¹ and A² each independentlyrepresent an alkyl group having 1 to 6 carbon atoms, an aryl grouphaving 6 to 12 carbon atoms, or an aralkyl group having 7 to 18 carbonatoms. m represents an integer of 1 or greater.

In the formula (3), as the alkylene group represented by R⁷, an alkylenegroup having 3 to 10 carbon atoms is preferable, and an alkylene grouphaving 3 to 6 carbon atoms is more preferable. The alkylene grouprepresented by R⁷ may have any one of a linear shape, a branched shape,or a cyclic shape, but preferably a linear shape.

If the number of carbons of the alkylene group represented by R⁷ is setto be 3 or greater, the decrease of the fluidity of the resincomposition is prevented, and thermoplasticity is easily exhibited. Ifthe number of carbons of the alkylene group represented by R⁷ is 10 orlower, or the alkylene group represented by R⁷ has a linear shape, theaffinity to the cellulose derivative is easily enhanced. Therefore, ifthe alkylene group represented by R⁷ has a linear shape, and the numberof carbons is in the range described above, moldability of the resincomposition is enhanced.

In this point of view, particularly, the alkylene group represented byR⁷ is preferably a n-hexylene group (—(CH₂)₆—). That is, the polyetherester compound is preferably a compound where R⁷ represents a n-hexylenegroup (—(CH₂)₆—).

In the formula (3), as the alkylene group represented by R⁸, an alkylenegroup having 3 to 10 carbon atoms is preferable, and an alkylene grouphaving 3 to 6 carbon atoms is more preferable. The alkylene grouprepresented by R⁸ may have any one of a linear shape, a branched shape,or a cyclic shape, but preferably a linear shape.

If the number of carbons of the alkylene group represented by R⁸ is 3 orgreater, the decrease of the fluidity of the resin composition isprevented, and the thermoplasticity is easily exhibited. If the numberof carbons of the alkylene group represented by R⁸ is 10 or lower, or ifthe alkylene group represented by R⁸ has a linear shape, the affinity tothe cellulose derivative is easily enhanced. Therefore, if the alkylenegroup represented by R⁸ has a linear shape, and the number of carbons isin the range described above, moldability of the resin composition isenhanced.

In this point of view, particularly, the alkylene group represented byR⁸ is preferably a n-butylene group (—(CH₂)₄—). That is, the polyetherester compound is preferably a compound where R⁸ represents a n-butylenegroup (—(CH₂)₄—).

In the formula (3), the alkyl groups represented by A¹ and A² are alkylgroups having 1 to 6 carbon atoms, and alkyl groups having 2 to 4 carbonatoms are more preferable. The alkyl groups represented by A¹ and A² mayhave anyone of a linear shape, a branched shape, or a cyclic shape, butpreferably a branched shape.

The aryl groups represented by A¹ and A² are aryl groups having 6 to 12carbon atoms, and as examples thereof, an unsubstituted aryl group suchas a phenyl group and a naphthyl group or a substituted phenyl groupsuch as a t-butylphenyl group and a hydroxyphenyl group are exemplified.

The aralkyl group represented by A¹ and A² is a group represented by—R^(A)-Ph. R^(A) represents a linear-shaped or branched alkylene grouphaving 1 to 6 carbon atoms (preferably, having 2 to 4 carbon atoms). Phrepresents an unsubstituted phenyl group or a substituted phenyl groupwhich is substituted with the linear-shaped or branched alkyl grouphaving 1 to 6 carbon atoms (preferably, having 2 to 6 carbon atoms). Asthe aralkyl group, specifically, for example, an unsubstituted aralkylgroup such as a benzil group, a phenylmethyl group (phenethyl group), aphenylpropyl group, and a phenylbutyl group, and a substituted aralkylgroup such as a methylbenzil group, a dimethylbenzil group, and amethylphenethyl group are exemplified.

At least one of A¹ and A² preferably represents an aryl group or anaralkyl group. That is, the polyether ester compound is preferably acompound where at least one of A¹ and A² represents an aryl group(preferably, phenyl group) or an aralkyl group, and preferably acompound where both of A¹ and A² represent an aryl group (preferably,phenyl group) or an aralkyl group.

Subsequently, characteristics of the polyether ester compound aredescribed.

The weight average molecular weight (Mw) of the polyether ester compoundis preferably in the range of 450 to 650, and more preferably in therange of 500 to 600.

If the weight average molecular weight (Mw) is 450 or greater, bleeding(phenomenon of deposition) becomes difficult. If the weight averagemolecular weight (Mw) is 650 or lower, the affinity to the cellulosederivative is easily enhanced. Therefore, if the weight averagemolecular weight (Mw) is in the range described above, moldability ofthe resin composition is enhanced.

In addition, the weight average molecular weight (Mw) of the polyetherester compound is a value measured by gel permeation chromatography(GPC). Specifically, the measurement of the molecular weight by GPC isperformed by using HPLC1100 manufactured by Tosoh Corporation as ameasurement apparatus, and TSKgel GMHHR-M+TSKgel GMHHR-M (7.8 mm I.D. 30cm) which is a column manufactured by Tosoh Corporation, with achloroform solvent. Also, the weight average molecular weight iscalculated by using a molecular weight calibration curve obtained by amonodispersed polystyrene standard sample from the measurement result.

The viscosity of the polyether ester compound at 25° C. is preferably inthe range of 35 mPa·s to 50 mPa·s, and more preferably in the range of40 mPa·s to 45 mPa·s.

If the viscosity is 35 mPa·s or greater, the dispersibility to thecellulose derivative is easily enhanced. If the viscosity is 50 mPa·s orlower, anisotropy of the dispersion of the polyether ester compoundhardly appears. Therefore, if the viscosity is in the range describedabove, the moldability of the resin composition is enhanced.

In addition, the viscosity is a value measured by an E-type viscosmeter.

A solubility parameter (SP value) of the polyether ester compound ispreferably in the range of 9.5 to 9.9, and more preferably in the rangeof 9.6 to 9.8.

If the solubility parameter (SP value) is in the range of 9.5 to 9.9,dispersibility to the cellulose derivative is easily enhanced.

The solubility parameter (SP value) is a value calculated by a Fedormethod, and specifically, the solubility parameter (SP value) is, forexample, calculated by the following equation in conformity with thedescription in Polym. Eng. Sci., vol. 14, p. 147 (1974).

SP value=√(Ev/v)=√(ΣΔei/ΣΔvi)  Equation:

In the equation, Ev: evaporation energy (cal/mol), v: molar volume(cm³/mol), Δei: evaporation energy of each atom or atom group, and Δvi:molar volume of each atom or atom group.

In addition, the solubility parameter (SP value) employs (cal/cm³)^(1/2)as a unit, but the unit is omitted in conformity with practice, and isdescribed in a dimensionless manner.

Hereinafter, specific examples of the polyether ester compound aredescribed, but the invention is not limited thereto.

R⁷ R⁸ A¹ A² Mw Viscosity (25° C.) APHA SP value PEE1 —(CH₂)₆— —(CH₂)₄—Phenyl group Phenyl group 550 43 120 9.7 PEE2 —(CH₂)₂— —(CH₂)₄— Phenylgroup Phenyl group 570 44 115 9.4 PEE3 —(CH₂)₁₀— —(CH₂)₄— Phenyl groupPhenyl group 520 48 110 10.0 PEE4 —(CH₂)₆— —(CH₂)₂— Phenyl group Phenylgroup 550 43 115 9.3 PEE5 —(CH₂)₆— —(CH₂)₁₀— Phenyl group Phenyl group540 45 115 10.1 PEE6 —(CH₂)₆— —(CH₂)₄— t-Butyl group t-Butyl group 52044 130 9.7 PEE7 —(CH₂)₆— —(CH₂)₄— Phenyl group Phenyl group 460 45 1259.7 PEE8 —(CH₂)₆— —(CH₂)₄— Phenyl group Phenyl group 630 40 120 9.7 PEE9—(CH₂)₆— —(CH₂)₄— Phenyl group Phenyl group 420 43 135 9.7 PEE10—(CH₂)₆— —(CH₂)₄— Phenyl group Phenyl group 670 48 105 9.7 PEE11—(CH₂)₆— —(CH₂)₄— Phenyl group Phenyl group 550 35 130 9.7 PEE12—(CH₂)₆— —(CH₂)₄— Phenyl group Phenyl group 550 49 125 9.7 PEE13—(CH₂)₆— —(CH₂)₄— Phenyl group Phenyl group 550 32 120 9.7 PEE14—(CH₂)₆— —(CH₂)₄— Phenyl group Phenyl group 550 53 105 9.7 PEE15—(CH₂)₆— —(CH₂)₄— Phenyl group Phenyl group 550 43 135 9.7 PEE16—(CH₂)₆— —(CH₂)₄— Phenyl group Phenyl group 550 43 105 9.7 PEE17—(CH₂)₆— —(CH₂)₄— Phenyl group Phenyl group 550 43 150 9.7 PEE18—(CH₂)₆— —(CH₂)₄— Phenyl group Phenyl group 550 43 95 9.7

Other Components

The resin composition according to the exemplary embodiment may containother components in addition to the components described above, ifnecessary. As the other components, for example, a flame retardant, acompatibilizer, an antioxidant, a release agent, a light resistantagent, a weather resistant agent, a colorant, pigments, a modifier, adrip preventing agent, an antistatic agent, a hydrolysis inhibitor, afiller, and a reinforcing agent (glass fiber, carbon fiber, talc, clay,mica, glass flake, milled glass, glass bead, crystalline silica,alumina, silicon nitride, aluminum nitride, boron nitride, and the like)are exemplified. The content of the respective components is in therange of 0% by weight to 5% by weight with respect to the total amountof the resin composition. Here, the expression “0% by weight” means notincluding other components.

The resin composition according to the exemplary embodiment may containother resins in addition to the resin described above. However, theother resins are included in amounts with which the ratio of thecellulose derivative occupied in the total amount of the resincomposition becomes in the range described above.

As the other resins, for example, the thermoplastic resins which arewell-known in the art are included. Specifically, polycarbonate resin;polypropylene resin; polyester resin; a polyolefin resin; polyestercarbonate resin; a polyphenylene ether resin; polyphenylene sulfideresin; a polysulfone resin; polyether sulfone resin; a polyaryleneresin; a polyetherimide resin; a polyacetal resin; a polyvinyl acetalresin; a polyketone resin; a polyetherketone resin; a polyether etherketone resin; a polyarylketone resin; a polyether nitrile resin; aliquid crystal resin; a polybenzimidazole resin; polyparabanic acidresin; a vinyl polymer or a vinyl copolymer resin obtained bypolymerizing or copolymerizing one or more vinyl monomers selected fromthe group consisting of an aromatic alkenyl compound, a methacrylic acidester, acrylic acid ester, and a vinyl cyanide compound; adiene-aromatic alkenyl compound copolymer resin; a vinylcyanide-diene-aromatic alkenyl compound copolymer resin; an aromaticalkenyl compound-diene-vinyl cyanide-N-phenylmaleimide copolymer resin;a vinyl cyanide-(ethylene-diene-propylene (EPDM))-aromatic alkenylcompound copolymer resin; a vinyl chloride resin; and a chlorinatedvinyl chloride resin are exemplified. These resins may be used singly,or two or more types thereof may be used in combination.

Method of Preparing Resin Composition

The resin composition according to the exemplary embodiment, forexample, may be prepared by molten-kneading the above-describedcellulose derivative or a mixture at least containing theabove-described cellulose derivative and the other components such asthe plasticizer. In addition, the resin composition according to theexemplary embodiment, for example, is prepared by dissolving theabove-described components in a solvent.

For molten-kneading, known machines may be used, and specific examplesthereof include a twin-screw extruder, a HENSCHEL MIXER, a BANBURYMIXER, a single-screw extruder, multi-screw extruder, and a co-kneader.

In addition, the temperature at the time of kneading may be determinedaccording to the melting temperature of the cellulose derivative used,but in view of the thermal decomposition and the fluidity, thetemperature in the range of 140° C. to 240° C. is preferable, and thetemperature in the range of 160° C. to 200° C. is more preferable.

Resin Molded Article

The resin molded article according to the exemplary embodiment includesthe resin composition according to the exemplary embodiment. That is,the resin molded article according to the exemplary embodiment is madeof the same composition as the resin composition according to theexemplary embodiment.

Specifically, the resin molded article according to the exemplaryembodiment may be obtained by molding the resin composition according tothe exemplary embodiment. As the molding method, injection molding,extrusion molding, blow molding, heat press molding, calendaringmolding, coating molding, cast molding, dipping molding, vacuum molding,transfer molding and the like may be applied.

As the method of molding the resin molded article according to theexemplary embodiment, since degrees of freedom in shape are high,injection molding is preferable. With respect to injection molding, theresin composition is heated and melted, casted into a mold, andsolidified, so as to obtain a molded article. The resin composition maybe molded by injection compression molding.

The cylinder temperature of the injection molding is, for example, inthe range of 140° C. to 240° C., preferably in the range of 150° C. to220° C., and more preferably in the range of 160° C. to 200° C. The moldtemperature of the injection molding is, for example, in the range of30° C. to 120° C., and more preferably in the range of 40° C. to 80° C.The injection molding may be performed, for example, by using acommercially available apparatus such as NEX500 manufactured by NisseiPlastic Industrial Co., Ltd., NEX150 manufactured by Nissei PlasticIndustrial Co., Ltd., NEX70000 manufactured by Nissei Plastic IndustrialCo., Ltd., and SE50D manufactured by Toshiba Machine Co., Ltd.

The resin molded article according to the exemplary embodiment may beappropriately used for the purposes of electric and electronicapparatuses, business machines, home appliances, automobile interiormaterials, engine covers, car bodies, containers, and the like. Morespecifically, the resin molded article may be used in housings ofelectric and electronic apparatuses or home appliances; variouscomponents of electric and electronic apparatuses or home appliances;interior components of automobiles; storage cases of CD-ROM, DVD, andthe like; food containers; drink bottles; food trays; wrappingmaterials; films; and sheets.

EXAMPLES

Hereinafter, the invention is described in greater detail with referenceto examples, but the invention is not limited to the examples. Inaddition, unless described otherwise, the expression “part” refers to“part by weight”.

Example 1

Depolymerization

50 g of powdered cellulose (manufactured by Nippon Paper Industries Co.,Ltd., KC FLOCK W-50GK) and 750 g of 1 mol/L hydrochloric acid (Wako PureChemical Industries, Ltd.) are added to a 1 L eggplant-shaped flask. Themixture is heated up until reflux while being stirred (rotational speedof 75 rpm to 100 rpm) by a stirrer, and is subjected to a refluxreaction for 2 hours. After cooling the reaction mixture, precipitatesare suction-filtered and washed with 600 ml of distilled water. Theobtained precipitates are vacuum-dried at 40° C. to obtain 47 g ofcellulose (white solid) (94% of yield).

The weight average molecular weight Mw of the obtained cellulose is25,000.

The molecular weight is measured by a GPC device (manufactured by TosohCorporation, HLC-8320GPC, column: TSKgelα-M) using a solution ofdimethylacetamide/lithium chloride having a weight ratio of 90/10.

Acetylation

500 g of glacial acetic acid is added to 100 g of the cellulose. Next, aliquid mixture of 500 g of glacial acetic acid (99.5% by weight) and 8.1g of sulfuric acid (96% by weight) is added thereto, and the mixture isstirred using a stirrer for 1 hour at room temperature. In this step,the ratio of the sulfuric acid to the cellulose corresponds to 7.8% byweight.

The reaction mixture is cooled with cold water (13° C.) and 500 g ofacetic anhydride (special grade, 97% by weight) is added dropwise whilestirring the mixture. The internal temperature is controlled to be lessthan or equal to 35° C. The cool bath is removed and the mixture isstirred for 4 hours at room temperature (RT, 24° C.) to obtain atranslucent white liquid.

After the stirring, the reaction liquid is cooled with cold water (8°C.). Then, a liquid mixture of 175.5 g of acetic acid and 75 g of wateris added dropwise for 30 minutes while being stirred (the internaltemperature is controlled to become less than or equal to 35° C.) and isstirred for 30 minutes at room temperature (24° C.). The reaction liquidis reprecipitated in purified water (10 L, stirred) of 5 times theamount of the reaction liquid, and is filtered under reduced pressureafter being stirred for 20 minutes to obtain white precipitates.

These white precipitates are dispersed in 10 L of purified water, andare filtered under reduced pressure after being stirred for 15 minutes.This washing step is repeated four times. In the filtrate of the finalwashing step, the pH is 6 and the electric conductivity is 26 μS/cm.

Drying is performed through freeze-drying to obtain 162 g of whitepowder (triacetate cellulose) (yield of 91%).

Deacetylation

960 g of acetic acid is added to 115.2 g of the obtained white powder(triacetate cellulose), and the mixture is stirred up until the whitepowder is completely dissolved. This solution is heated to 40° C., and236.1 g of a 2.54% by weight aqueous hydrochloric acid solution is addedto the solution for 30 minutes. Then, the mixture is stirred for 15hours at 40° C. A supernatant component of the reaction solution isreprecipitated in 8 L of purified water (stirred), and is filtered underreduced pressure after being stirred for 20 minutes, while removingprecipitates in the reaction solution through a decantation method.White precipitates are obtained in this manner.

These white precipitates are dispersed in 8 L of purified water, and arefiltered under reduced pressure after being stirred for 15 minutes. Thiswashing step is repeated three times. In the filtrate of the finalwashing step, the pH is 6 and the electric conductivity is 26 μS/cm.

Drying is performed through freeze-drying to obtain 93 g of white powder(diacetate cellulose powder) (yield of 88%).

As a result of a ¹H-NMR measurement (DMSO-d₆, 40° C.), the averagedegree of substitution of the diacetate cellulose powder is 2.34 and theweight average molecular weight Mw is 40,000.

Measurement of Insoluble Portion with Respect to Tetrahydrofuran (THF)

10.0 g of THF is added to 1.000 g of the diacetate cellulose powder. Thesolution is tightly closed and is stirred for 24 hours at 25° C., and isthen allowed to stand for 24 hours. After separating a supernatantsolution from the solution, 10.0 g of THF is added to the remainingprecipitate portion. The solution of the precipitate portion is tightlyclosed and is stirred for 24 hours at 25° C., and is then allowed tostand for 24 hours. A precipitate portion that has not been dissolved inTHF is taken by filtering and is washed with 10.0 g of THF. Then, theprecipitate portion is vacuum-dried.

The yield, that is, the amount of a THF insoluble portion is 20 mg, andthe weight ratio is 2% by weight.

In addition, as a result of a ¹H-NMR measurement (DMSO-d₆, 40° C.), theaverage degree of substitution of the THF insoluble portion is 2.51.

Measurement of Insoluble Portion with Respect to Dimethyl Sulfoxide(DMSO)

10.0 g of DMSO is added to 1.000 g of the diacetate cellulose powder.The solution is tightly closed and is stirred for 24 hours at 25° C.,and is then allowed to stand for 24 hours. After separating asupernatant solution from the solution, 10.0 g of DMSO is added to theremaining precipitate portion. The solution of the precipitate portionis tightly closed and is stirred for 24 hours at 25° C., and is thenallowed to stand for 24 hours. A precipitate portion that has not beendissolved in DMSO is taken by filtering and is washed with 10.0 g ofmethylene chloride. Then, the precipitate portion is vacuum-dried.

The yield, that is, the amount of a DMSO insoluble portion is 7 mg, andthe weight ratio is 0.7% by weight.

In addition, as a result of a ¹H-NMR measurement (DMSO-d₆, 40° C.), theaverage degree of substitution of the DMSO insoluble portion is 1.20.

Ca Stabilizer

70 g of the diacetate cellulose powder is dispersed in 700 g of purifiedwater, 0.2 g of calcium acetate monohydrate is added thereto, and themixture is stirred for 18 hours at room temperature (24° C.) to obtainwhite precipitates. The white precipitates are filtered under reducedpressure and are dried through freeze-drying to obtain white powder.

Kneading

The diacetate cellulose powder after being subjected to theCa-stabilizing processing is kneaded by a biaxial kneading device(manufactured by Toshiba Machine Co., Ltd., TEX41SS) at 230° C. toobtain resin composition pellets.

Injection Molding

Regarding the obtained pellets, an ISO multipurpose dumbbell test piece(100 mm of the length of a test portion, 10 mm of the width thereof, and4 mm of the thickness thereof) is manufactured using an injectionmolding machine (manufactured by Nissei Plastic Industrial Co., Ltd.,PNX40) at cylinder temperature of 230° C. and mold temperature of 40° C.

Evaluation Test

Bending Elastic Modulus

The bending elastic modulus of the obtained ISO multipurpose dumbbelltest piece is measured through a method according to ISO-178 using auniversal tester (manufactured by Shimadzu Corporation, AUTOGRAPHAG-Xplus). In addition, the tensile strength is measured using the samedevice.

Examples 2 to 5

Diacetate cellulose is prepared in the same manner as in Example 1except that the reaction conditions of the “depolymerization”, the“acetylation” and the “deacetylation” are changed as shown in Table 1,and evaluation is performed. The results are shown in Table 1.

Comparative Examples 1 to 5

Diacetate cellulose is prepared in the same manner as in Example 1except that the reaction conditions of the “depolymerization”, the“acetylation” and the “deacetylation” are changed as shown in Table 1,and evaluation is performed. The results are shown in Table 1.

TABLE 1 Performance of molded [Depolymer- [Deacetylation] AverageInsoluble product ization] 2.54 parts by degree of Weight portion in THFBending Reflux time weight of substi- average Average Insoluble elasticTensile in 1M hydro- hydrochloric tution molecular Content degree ofportion modulus strength chloric acid [Acetylation] acid (NMR) weightrate substitution in DMSO (MPa) (Mpa) Example 1 2 h Sulfuric acid 7.8%40° C./15 h 2.34 40,000  2% 2.51 0.7% 4400 58 by weight, RT/4 h Example2 1 h Sulfuric acid 7.8% 40° C./15 h 2.36 47,000  2% 2.53 0.6% 4800 68by weight, RT/4 h Example 3 0.5 h  Sulfuric acid 7.8%  40° C./16.5 h2.23 56,000 1.5%  2.51 0.8% 5600 75 by weight, RT/4 h Example 4 2 hSulfuric acid 7.8%  40° C./12.5 h 2.45 42,000  3% 2.58 0.5% 4300 60 byweight, RT/4 h Example 5 1 h Sulfuric acid 17.3% 23° C./48 h 2.38 47,0001.0%  2.55 0.6% 4800 67 by weight, RT/3 h Comparative 2 h Sulfuric acid1.7% 41° C./14 h 2.47 36,000 28% 2.77 2.5% 900 14 Example 1 by weight,RT/5 h Comparative 1 h Sulfuric acid 1.7% 41° C./14 h 2.46 46,000 29%2.75 2.6% 1100 16 Example 2 by weight, RT/5 h Comparative 0.5 h Sulfuric acid 1.7% 41° C./14 h 2.48 56,000 30% 2.78 2.7% 1200 18 Example3 by weight, RT/5 h Comparative 0.5 h  Sulfuric acid 5.0% 40° C./15 h2.38 55,000 12% 2.74 1.6% 1600 24 Example 4 by weight, RT/5 hComparative 0.5 h  Sulfuric acid 5.6% 40° C./15 h 2.36 55,000  8% 2.701.3% 1800 26 Example 5 by weight, RT/5 h

It may be seen that Examples 1 to 5 which contains a cellulosederivative, in which the weight average molecular weight is 10,000 to75,000, the average degree of substitution of an acyl group is 1.8 to2.5, and in which the amount of an insoluble portion (THF insolubleportion) of this cellulose derivative when being dissolved intetrahydrofuran (THF) at 25° C. satisfies the range are excellent in thebending elastic modulus and the tensile strength compared to ComparativeExamples 1 to 5 in which the amount of a THF insoluble portion of acellulose derivative is out of the range.

The foregoing description of the exemplary embodiments of the presentinvention has been provided for the purposes of illustration anddescription. It is not intended to be exhaustive or to limit theinvention to the precise forms disclosed. Obviously, many modificationsand variations will be apparent to practitioners skilled in the art. Theembodiments were chosen and described in order to best explain theprinciples of the invention and its practical applications, therebyenabling others skilled in the art to understand the invention forvarious embodiments and with the various modifications as are suited tothe particular use contemplated. It is intended that the scope of theinvention be defined by the following claims and their equivalents.

1. A resin composition comprising: a cellulose derivative in which atleast one hydroxyl group is substituted with an acyl group, thecellulose derivative having a weight average molecular weight of 20,000to 75,000 and an average degree of substitution of the acyl group of 1.8to 2.5, and which exhibits an amount (weight ratio) of an insolubleportion, when being dissolved in tetrahydrofuran (THF) at 25° C., ofless than or equal to 5% by weight, and an adipic acid ester-containingcompound.
 2. The resin composition according to claim 1, wherein theamount (weight ratio) of the insoluble portion of the cellulosederivative when being dissolved in dimethyl sulfoxide (DMSO) at 25° C.is less than or equal to 1% by weight.
 3. The resin compositionaccording to claim 1, wherein a ratio of the cellulose derivativeoccupied in the total amount of the resin composition is greater than orequal to 70% by weight.
 4. The resin composition according to claim 2,wherein a ratio of the cellulose derivative occupied in the total amountof the resin composition is greater than or equal to 70% by weight.
 5. Aresin composition comprising: a cellulose derivative in which at leastone hydroxyl group is substituted with an acyl group, the cellulosederivative having a weight average molecular weight of 10,000 to 75,000and an average degree of substitution of the acyl group of 1.8 to 2.5,and which exhibits an amount (weight ratio) of an insoluble portion,when being dissolved in tetrahydrofuran (THF) at 25° C., of less than orequal to 5% by weight, and an adipic acid ester-containing compound.6.-8. (canceled)
 9. The resin composition according to claim 1, whereinthe acyl group is an acetyl group.
 10. The resin composition accordingto claim 2, wherein the acyl group is an acetyl group.
 11. The resincomposition according to claim 3, wherein the acyl group is an acetylgroup.
 12. The resin composition according to claim 5, wherein the acylgroup is an acetyl group.
 13. A resin molded article comprising a resincomposition comprising a cellulose derivative in which at least onehydroxyl group is substituted with an acyl group, the cellulosederivative having a weight average molecular weight of 10,000 to 75,000and an average degree of substitution of the acyl group of 1.8 to 2.5,and which exhibits an amount (weight ratio) of an insoluble portion,when being dissolved in tetrahydrofuran (THF) at 25° C., of less than orequal to 5% by weight, and an adipic acid ester-containing compound. 14.A resin molded article comprising the resin composition according toclaim
 2. 15. A resin molded article comprising the resin compositionaccording to claim
 3. 16. (canceled)
 17. A resin molded articlecomprising the resin composition according to claim
 9. 18. The resinmolded article according to claim 13, which is an injection moldedarticle.
 19. (canceled)